The grails database migration plugin

Grails has a comprehensive guide on how to use the database-migration plugin for your greenfield Grails projects. The guide however does not explain clearly how to go about this with an existing app. This blog post details how to setup it up in that scenario.

The first thing is to set your datasource dbCreate property to none in the application.yml:

dataSource:
          dbCreate: none

And install the plugin as mentioned in the guide. With the plugin installed and the migrations folder location setup in build.gradle the next step is to create the changelog.groovy file. Instead of running the:

$ grails dbm-generate-gorm-changelog

or

$ grails dbm-generate-changelog grails

commands to create changelog.groovy based on your GORM classes or database respectively run:

$ grails dbm-create-changelog changelog.groovy

This creates an empty changelog.groovy file eliminating the need to sync the current state of the database with the plugin’s migrations tracking tables. The only thing left is to create the DATABASECHANGELOG and DATABASECHANGELOGLOCK tables in the database. You can either run:

$ grails dbm-update

Or more appropriately setup such that migrations are run on startup:

grails-app/conf/application.yml

grails:
    plugin:
        databasemigration:
            updateOnStart: true
            updateOnStartFileName: changelog.groovy

And then just run:

$ grails run-app

Which will create the two tables in the database on the first run. From here on in you can proceed as normal and create change sets manually.

You can find a simple app illustrating this on github.